I own an 82 300SD. The temp sensor is above the rear view mirror in the center of the head liner. You should have a small square hole with a grill on it made of plastic. It is right before the sunroof (if you have one). Since you changed the monovalve, I am not sure what the problem may be. When I bought mine, I replaced the monovavle, but also had intermittent operation of the fan and such do to the ACC. I purchased a rebuilt unit and everything cleared up. If your ACC is the original, then you may be having trouble with the flex circuits. Over time they fail and cause intermittent operation. Hope this helps.

My guess is if you have to check that temperature sensor, you would have to remove the headliner to get to it. My best guess is that it is not the temp sensor. I did a search in the threads and could not find any one with problems with the temp sensor on a 300SD at the time.

Good luck.

Rob

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'82 300SD 206K miles Anthracite Grey received 250,000 Km badge
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